The present invention relates to a device for transmission between a primary motor shaft and an output shaft, such as a drive shaft for the wheels of a self-propelled machine, such as lawn mowers.
It relates more particularly to a transmission device comprising at least, disposed at least partially within a casing constituted by two half shells assembleable on a joint plane, a reducing mechanism constituted by a driving member, such as an endless screw, and a driven member, such as a tangent toothed wheel, mounted on the output shaft, the driving member being held in position within the casing by means of bearings provided in each half shell, these bearings being disposed facing each other in the assembled condition of the two half shells.
Such devices are at present well known to those skilled in this art and are widely used particularly for the transmission of movement between the primary motor shaft that carries the lawn mower blade, and the output shaft of the wheels of said mower. In devices known at present, each bearing adapted to receive one end of the endless screw, is a ball bearing. The presence of ball roller ways permits receiving, independently of the direction of rotation of the toothed wheel, the axial forces to which the endless screw is subjected under the action of the toothed wheel. However, such pieces are cumbersome.
An object of the present invention is to provide a transmission device whose design permits replacing a roller bearing adapted to receive one end of the endless screw, by a smooth bearing so as to permit omitting ball roller ways so as to reduce the cost of such a device.
To this end, the invention has for its object a transmission device between a primary motor shaft and an output shaft, such as a drive shaft for the wheels of self-driven machines, such as lawn mowers, this device comprising at least, disposed at least partially within a casing constituted by two half shells assembleable along a joint plane, a reducing mechanism constituted by a driving member, such as an endless screw, and a driven member, such as a tangent toothed wheel, mounted on the output shaft, the driving member being held in position by means of bearings provided in each half shell, these bearings being disposed facing each other in the assembled condition of the half shells, characterized in that one end of the endless screw is disposed in a smooth bearing of a half shell of the casing, and in that it is provided adjacent this bearing, generally on opposite sides of this bearing, with at least one, preferably two, cross members that bear on a wall, preferably the bottom wall, of the half shell and extending in the direction of the bearing of the opposite half shell to bear, in the assembled condition of the half shells, against the radial surface of a roller way, preferably a ball bearing, which is part of said bearing, the end of the endless screw, supported by the roller bearing, being immobilized axially by at least one stop means, the axial forces, borne by the endless screw under the action of the tangent toothed wheel, being neutralized by the presence of these cross pieces.
The invention also has for its object a self-propelled lawn mower of the type comprising, between its primary motor shaft and the output shaft for driving the wheels of the mower, a transmission device, characterized in that the transmission device is according to the above described device.